<?hh
/* Prototype  : proto string preg_replace(mixed regex, mixed replace, mixed subject [, int limit [, count]])
 * Description: Perform Perl-style regular expression replacement.
 * Source code: ext/pcre/php_pcre.c
 * Alias to functions:
*/
<<__EntryPoint>> function main(): void {
$string = '123456789 - Hello, world -           This is a string.';
var_dump($string);

var_dump(preg_replace('<- This is a string$>',
                      'This shouldn\'t work', $string));                //tries to find '- This is a string' at the end of a string but can't so replaces nothing and prints the unchanged $string.

$count = -1;
var_dump(preg_replace_with_count('<[0-35-9]>',
                                 '4', $string,                                   //finds any number that's not 4 and replaces it with a 4
                                 5, inout $count));                            //limits to 5 replacements returns 444444789
var_dump($count);                                            //counts the number of replacements made (5)


var_dump(preg_replace('<\b[hH]\w{2,4}>',
                      'Bonjour', $string));                        //finds h or H at the beginning of a word followed by 2-4 characters and replaces it with Bonjour (i.e. Hello -> Bonjour) (was finding the 'his' in This and replacing it)

var_dump(preg_replace('<(\w)\s*-\s*(\w)>',
                      '\\1. \\2', $string));                        //finds dashes with an indefinite amount of whitespace around them and replaces them with a full stop precedeby no spaces and followed by one space

var_dump(preg_replace('<(^[a-z]\w+)@(\w+)\.(\w+)\.([a-z]{2,}$)>',
                      '\\1 at \\2 dot \\3 dot \\4', 'josmessa@uk.ibm.com'));    //finds the e-mail address and replaces the @ and . with "at" and "dot" (uses backreferences) ('josmessa at uk dot ibm dot com')
}
